The present invention relates generally to the field of printing. More specifically, the present invention provides methods and apparatus for sensing a paper low condition for fan-folded tickets in a ticket printer.
In an example of the prior art as shown in FIG. 1, a reflective sensor 2 is mounted to the side 3 of a paper tray 4 which can hold a stack of fan-folded tickets. A light emitting diode (LED) of the reflective sensor 2 shines light onto the side of the stack of tickets. If the light from the LED reflects off of the ticket stack, then that light will return to a phototransistor inside the reflective sensor 2. In this case, the printer will not report a paper low condition. If the light from the LED does not reflect off of the ticket stack, then that light will not return to the phototransistor inside the reflective sensor. In this case, the printer will report a paper low condition.
One problem with this method of sensing a paper low condition is that the printer will typically report a paper low condition when there are twenty to forty tickets left in the paper tray 4. The critical specification for a reflective object sensor is the distance between the sensor and the object to be sensed. The paper tray 4 is wider than the tickets in order to accommodate the ticket width tolerance. Therefore, if the tickets are biased towards the paper tray side 6 that is furthest away from the sensor 2, then the distance from the sensor 2 to the tickets will be, for example, approximately 0.08 inches greater than if the tickets were biased towards the paper tray side 3 that is closest to the sensor 2. This complicates the sensor design and could lead to paper low sensing failures.
Further, reflective object sensors are not designed to sense small objects. The typical ticket thickness is approximately 0.005 inches. When the sensor 2 is mounted to the side 3 of the paper tray 4, it cannot accurately sense how many tickets are left in the paper tray. One sensor may indicate that paper is low when there are 30-40 tickets left in the paper tray. Another sensor may indicate that paper is low when there are 10-20 tickets left in the paper tray. Therefore, if the operator puts a new stack of fan-folded tickets into the paper tray after receiving the paper low message, the operator will end up discarding a large number of unused tickets. Such an implementation is wasteful of resources.
It would be advantageous to provide methods and apparatus for sensing a paper low condition for fan-folded tickets in a ticket printer which indicates a paper low condition when only one or two tickets remain in the ticket printer, to avoid wasting unused tickets.
The methods and apparatus of the present invention provide the foregoing and other advantages.